For stark white icing I just use the Wilton class buttercream recipe that uses all Criso. I do add the flavored oil instead of the vanilla extract. I can't really tell you how much I add because I just add it in. Yes, the Lorann oils are those little bottles. They come in all flavors, but I am so hooked on the Bavarian Cream that I haven't tried anything else yet.
As for an off-white recipe, I use 1/2 Crisco and 1/2 butter along with the Bavarian Cream. This is my favorite icing to use, but because of the butter, it gives it an off-white color. I can't use it when the bride wears pure white.
Hope this helps. Let us know if you have anymore questions.
FAITH sees the invisible, believes the incredible, receives the impossible!
FAITH sees the invisible, believes the incredible, receives the impossible!